Alignment of antenna polarization axes

Description

FIELD AND BACKGROUND OF THE INVENTION

[0001] The present invention relates to alignment of antenna polarization axes and, in particular, it concerns alignment of antenna polarization axes of a dual polarized end-user terminal.

[0002] Geostationary satellite transponders are in common orbit 23,000 miles above the earth. The satellites share common latitude on the equator and are spaced apart longitudinally in an orbital arc, called the Clark belt, sometimes by less than one degree. When communicating with these satellites care must be taken not to illuminate more than one satellite with up-link radio frequency energy and, conversely, not to receive interfering signals from adjacent satellites located along the Clark belt. A satellite communicates using various frequencies to maximize the communication capacity of the satellite. Moreover, a satellite also typically communicates in two polarization axes, being orthogonal to each other, to maximize the capacity of each available frequency. Regulatory authorities, such as the FCC and ETSI require that the end-user terminal be aligned very accurately with the satellite. The regulations require that other satellites and also a non-designated polarization axis of the designated satellite will not receive even a component of the transmitted signal from the end-user terminal that exceeds a very low threshold. Therefore it is essential for the azimuth, elevation and polarization alignment of the end-user terminal to be aligned accurately. As is known in the art, azimuth and elevation alignment can be performed by adjusting the antenna direction of the end-user terminal to maximize the received signal from the designated satellite. This is known as the signal strength pointing method. Similar adjustment for polarization alignment does not yield satisfactory results and another method must be, employed. The current method for polarization adjustment includes the installer sending a linearly polarized test signal from the end-user terminal to the satellite. The test signal is received by the satellite. A component of the test signal is received in one polarization axis of the satellite and another component of the test signal is received in the other polarization axis of the satellite. The magnitude of the components in each axis is received by the satellite control center. The installer telephones the control center for the results and then adjusts the antenna polarization. Another test signal is sent to the satellite and the process continues until the antenna polarization is aligned with the satellite. This process is very difficult, time consuming and not accurate. Moreover, the designated frequency in both polarization axes of the satellite cannot be used for normal communications during this alignment process.

[0003] Document EP 1 303 002 discloses a method for the polarization alignment of an antenna of an earth station with the polarization axis of the antenna of a satellite by processing the satellite beacon signal in order to get a measure of misalignment.

[0004] Document US 5 568 158 describes electronic circuitry which adjusts the polarization of an antenna feed to match the polarization of an incoming signal in order to maximize the signal to noise ratio.

[0005] There is therefore a need for a system and method of aligning antenna polarization axes of a dual polarized end-user terminal.

SUMMARY OF THE INVENTION

[0006] The present invention is a system and method of aligning antenna polarization axes of a dual polarized end-user terminal.

[0007] According to the teachings of the present invention there is provided, a method for aligning antenna polarization axes of a dual polarized end-user terminal having an antenna, the antenna being aligned with a satellite in relation to azimuth and elevation, the end-user terminal being configured to produce a first output corresponding to a first component of a received signal parallel to a first polarization axis of the antenna and a second output corresponding to a second component of the received signal parallel to a second polarization axis of the antenna, the first polarization axis being orthogonal to the second polarization axis, the method comprising the steps of: (a) receiving a linearly polarized signal having a frequency wherein for the frequency and during a time period when the signal is being transmitted, the satellite is not transmitting signals with a linear polarization that is orthogonal to the linearly polarized signal; (b) autocorrelating first output and the second output such that, only correlating terms of the first output and the second output are multiplied together producing a measurement of autocorrelation; and (c) adjusting the antenna polarization axes to minimize the measurement of autocorrelation.

[0008] According to a further feature of the present invention, the step of autocorrelating is performed by inputting the first output and the second output into an electronic mixer to produce the measurement of autocorrelation.

[0009] According to a further feature of the present invention, there is also provided the step of reducing proportionately frequencies of the first output and the second output.

[0010] According to a further feature of the present invention, there is also provided the step of tuning the first output and the second output to the frequency.

[0011] According to a further feature of the present invention, there is also provided the step of filtering the first output using a first band pass filter and the second output using a second band pass filter.

[0012] According to a further feature of the present invention, the step of autocorrelating is performed by inputting the first output and the second output into an electronic mixer and inputting the output of the electronic mixer into a low-pass filter to produce the measurement of autocorrelation.

[0013] According to a further feature of the present invention, there is also provided after the step of autocorrelating, the step of displaying the measurement of autocorrelation.

[0014] According to a further feature of the present invention, the step of adjusting is performed by actuating an alignment actuator configured to adjust the antenna polarization axes to minimize the measurement of autocorrelation.

[0015] According to the teachings of the present invention there is also provided, a system for aligning antenna polarization axes of a dual polarized end-user terminal having an antenna, the antenna being aligned with a satellite in relation to azimuth and elevation, the end-user terminal being configured to produce a first output corresponding to a first component of a received signal parallel to a first polarization axis of the "antenna and a second output corresponding to a second component of the received signal parallel to a second polarization axis of the antenna, the first polarization axis being orthogonal to the second polarization axis, the system comprising: (a) a first connection configured for connection to the end-user terminal for receiving the first output; (b) a second connection configured for connection to the end-user terminal for receiving the second output; and (c) an autocorrelation apparatus having a first input and a second input; said first connection being connected to the first input, said second connection being connected to said second input, said autocorrelation apparatus being configured for autocorrelating the first output and the second output such that only correlating terms of the first output and the second output are multiplied together producing a measurement of autocorrelation.

[0016] According to a further feature of the present invention, the autocorrelation apparatus includes an electronic mixer having a first input that is connected to the first connection and a second input that is connected to the second connection.

[0017] According to a further feature of the present invention: (a) the autocorrelation apparatus further includes a low-pass filter having an input; and (b) the electronic mixer has an output that is connected to the input of the low-pass filter.

[0018] According to a further feature of the present invention: (a) the low-pass filter has an output; and (b) the input of the display is connected to the output of the low-pass filter.

[0019] According to a further feature of the present invention: (a) the autocorrelation apparatus further includes a dual polarized block down-converter having a first input that is connected to the first connection and a second input that is connected to the second connection; and (b) the dual polarized block down-converter is interposed between the first connection, the second connection and the electronic mixer.

[0020] According to a further feature of the present invention, there is also provided: (a) a first down-converter that is interposed between the first connection and the electronic mixer; and (b) a second down-converter that is interposed between the second connection and the electronic mixer.

[0021] According to a further feature of the present invention, the autocorrelation apparatus includes: (a) a first tuner that is interposed between the first connection and the electronic mixer; and (b) a second tuner that is interposed between the second connection and the electronic mixer.

[0022] According to a further feature of the present invention, the autocorrelation apparatus includes: (a) a first band pass that is interposed between the first connection and the electronic mixer; and (b) a second band pass filter that is interposed between the second connection and the electronic mixer.

[0023] According to a further feature of the present invention, there is also provided an alignment control system and an alignment actuator wherein the alignment control system is configured to control the alignment actuator to adjust the antenna polarization axes in response to an output of the autocorrelation apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein:

Fig. 1 is a schematic orthogonal view of a linearly polarized signal being received from a satellite by an end-user terminal in alignment mode that is constructed and operable in accordance with a preferred embodiment of the invention;

Fig. 2 is a schematic plan view of the linearly polarized signal being received by the end-user terminal of Fig. 1;

Fig. 3 is a schematic view of an alignment equipment setup for use with the end-user terminal of Fig. 1;

Fig. 4 is a schematic representation of the operation of an autocorrelation apparatus for use with the end-user terminal of Fig. 1;

Fig. 5 is a table comparing the system of Fig. 4 to a signal strength system of polarization alignment;

Fig. 6 is a schematic representation of the operation of an alignment control system for use with the autocorrelation apparatus of Fig. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The present invention is a system and method of aligning antenna polarization axes of a dual polarized end-user terminal.

[0026] The principles and operation of a system and method of aligning antenna polarization axes of a dual polarized end-user terminal according to the present invention may be better understood with reference to the drawings and the accompanying description.

[0027] Reference is now made to Fig. 1 and 2. Fig. 1 is a schematic orthogonal view of an end-user terminal 10 receiving a linearly polarized signal 15 from a satellite 20 in alignment mode that is constructed and operable in accordance with a preferred embodiment of the invention. Fig. 2 is a schematic plan view of the end user terminal 10 receiving linearly polarized signal 15. End-user terminal has an antenna 17. Antenna 17 includes a reflector 18 and an antenna feed 19. End-user terminal 10 is dual polarized meaning that antenna 17 has an associated polarization axis, known in the art as co-polarization axis 25 and an associated polarization axis, known in the art as cross polarization axis 30. Co-polarization axis 25 is orthogonal to cross polarization axis 30. End-user terminal 10 is configured to produce an output corresponding to a component of a received signal parallel to co-polarization axis 25. End-user terminal 10 is also configured to produce another output corresponding to a component of a received signal parallel to cross-polarization axis 30.

[0028] Before polarization alignment commences antenna 17 is aligned with satellite 20 in relation to azimuth and elevation. Polarization axes 25, 30 are aligned as close as possible with the polarization axes of satellite 20. Typically, this initial polarization is within 5 degrees of the optimal polarization. The alignment process now commences. Antenna 17 receives linearly polarized signal 15. Signal 15 is transmitted at a known frequency. In fact, signal 15 is typically a modulated signal having a range of frequencies. Therefore, the term frequency refers to a range of frequencies or frequency band. During the time period of the alignment process it is important that for the frequency of signal 15, satellite 20 is not transmitting signals with a linear polarization that is orthogonal to the linear polarization of signal 15. End-user terminal 10 produces an output 40 corresponding to a component 45 of signal 15 received parallel to co-polarization axis 25 and an output 50 corresponding to a component 55 of signal 15 received parallel to cross polarization axis 30. Output 40 and output 50 are autocorrelated and produce a measurement of autocorrelation. Output 40 and output 50 may contain signals and other than signal 15. Therefore, by autocorrelating output 40 and output 50, only parts of output 40 and output 50 that contain signal 15 will be multiplied together to produce the measurement of autocorrelation. Therefore, the measurement of autocorrelation gives a measurement of the alignment of polarization axes 25, 30 to the polarization axis of signal 15. Therefore, the measurement of autocorrelation gives a measurement of the alignment of polarization axes 25, 30 to the polarization axes of satellite 20. As the polarization axis of signal 15 becomes more parallel to co-polarization axis 25, component 45 increases and component 55 decreases and therefore the measurement of autocorrelation decreases. When the polarization axis of signal 15 is parallel to co-polarization axis 25, the measurement of autocorrelation will be zero. Polarization axes 25, 30 of antenna 17 are adjusted to minimize the measurement of autocorrelation. The above method of alignment enables accurate and quick alignment of antenna polarization without the need to send a signal to the satellite and to telephone the control center to receive adjustment data.

[0029] Reference is now made to Fig. 3, which is a schematic view of an alignment equipment setup 60 for use with end-user terminal 10. Alignment equipment setup 60 includes an autocorrelation apparatus 65 that autocorrelates output 40 and output 50. Autocorrelation apparatus 65 is explained in more detail with reference to Fig. 4. Alignment equipment setup 60 also includes a display device, typically being a digital voltmeter (DVM) 70, for displaying the measurement of autocorrelation calculated by autocorrelation apparatus 65. Polarization axes 25, 30 are adjusted, typically manually, to minimize the reading of voltmeter 70. It should be noted the measurement of autocorrelation could be processed to enable display by other methods and these methods might not include the use of a digital voltmeter to display the result. Alternatively, the output of autocorrelation apparatus 65 is directly connected to an alignment control system 75. Alignment control system 75 is configured to operate an alignment actuator 80. Alignment actuator 80 adjusts polarization axes 25, 30. Alignment actuator 80 is typically a system of fluid operated or motorized actuators that adjust at least one of reflector 18 and antenna feed 19. Alignment control system 75 is explained in more detail with reference to Fig. 6.

[0030] Reference is now made to Fig. 4, which is a schematic representation of the operation of autocorrelation apparatus 65. Autocorrelation apparatus 65 includes a dual polarized low noise block down-converter (LNB) 85. Block down-converter 85 typically forms part of end-user terminal 10 and is located close to antenna feed (FEED) 19. Output 40 and output 50 are inputs of block down-converter 85. Block down-converter 85 reduces proportionately all frequencies contained within output 40 and output 50 from Ku-band or C-band to L-band. Block-down converter 85 produces an output 90 corresponding to down-converted output 40 and an output 95 corresponding to a down-converted output 50. One output terminal of block down-converter 85 is connected to the input terminal of a tuner 100 and the other output terminal of block down-converter 85 is connected to the input terminal of a tuner 105. Output 90 is input to tuner 100 and output 95 is input to tuner 105. Tuner 100 tunes output 90 to the down-converted frequency of signal 15. Tuner 105 tunes output 95 to the down-converted frequency of signal 15. Tuner 100 and tuner 105 also down-converts the frequencies contained within output 90 and output 95 from L-band to IF-band. Tuner 100 produces an output 110. Tuner 105 produces an output 115. The output terminal of tuner 100 is connected to the input terminal of a band-pass filter (BPF) 120. The output terminal of tuner 105 is connected to the input terminal of a band-pass filter 125. Band-pass filters 120, 125 typically have a pass band that is in the range of 6 MHz to 8 MHz wide. Band-pass filters 120, 125 reject unwanted noise received by antenna 17 at the edges of the frequency band of signal 15. Band-pass filter 120 produces an output 130. Band-pass filter 125 produces an output 135. The output terminal of band-pass filter 120 is connected to the input terminal of a variable attenuator 140. The output terminal of variable attenuator 140 is connected to the input terminal of a variable gain amplifier 145. The output terminal of band-pass filter 125 is connected to the input terminal of a variable attenuator 150. The output terminal of variable attenuator 150 is connected to the input terminal of a variable gain amplifier 155. Output 130 is amplified by variable gain amplifier 145 and adjusted in level by variable attenuator 140 to produce an output 160. Output 160 has a signal level in the range of 0 dBm to 15 dBm to comply with the working range of a double balanced mixer 165 in the next stage of autocorrelation apparatus 65. Output 135 is amplified by variable gain amplifier 155 and adjusted in level by variable attenuator 150 to produce an output 170. Output 170 has a signal level in the range of 0 dBm to 15 dBm to comply with the working range of double balanced mixer 165 in the next stage of autocorrelation apparatus 65. Double balanced mixers are commercially available, for example, from Mini Circuits, Brooklyn, New York. The output terminal of variable gain amplifier 145 is connected to a first input terminal of double balanced mixer 165. The output terminal of variable gain amplifier 155 is connected to a second input terminal of double balanced mixer 165. Double balanced mixer 165 produces an output 175 that contains a low frequency component and a high frequency component. The low frequency component of output 175 is proportional to the multiplication of correlating terms of output 160 and output 170. The high frequency component of output 175 is proportional to non-correlating terms of output 160 and 170 and to the multiplication of correlating terms of output 160 and output 170. The output terminal of double balanced mixer 165 is connected to the input terminal of a low-pass filter (LPF) 180. Low-pass filter 180 is typically in the range 1 Hz to 10 Hz. Low-pass filter 180 produces an output 185 that contains the low frequency component of output 175. Output 185 is therefore the measurement of autocorrelation of output 40 and output 50.

[0031] It should be noted that substitute components are typically available for use in autocorrelation apparatus 65 to provide the same functionality as the components mentioned above. Moreover, the components of autocorrelation apparatus 65 may be assembled in a different order and some may be omitted entirely. For example if a higher frequency mixer is available it is possible to remove some or all of the down-converters. In addition, the amplifiers and attenuators may not be needed.

[0032] The output terminal of low-pass filter 180 is connected to the input terminal of digital voltmeter 70 for displaying the measurement of autocorrelation calculated by autocorrelation apparatus 65. Alternatively, the output terminal of low-pass filter 180 is connected to the input terminal of alignment control system 75.

[0033] Reference is now made to Fig. 5, which is a table comparing the system of Fig. 4 to a signal strength system of polarization alignment. Following is an algebraic treatment comparing the autocorrelation method using autocorrelation apparatus 65 of Fig. 4 to the traditional signal-strength system of polarization alignment. It should be noted that the following algebraic treatment is presented to facilitate a more complete understanding of the system of Fig. 4 and is not in any way limiting the scope of the invention as defined by the claims appended hereto.

[0034] At optimal alignment of the antenna polarization axes 25, 30 towards satellite 20 the level of output 185 is zero. At a small error rotation angle Δθ from optimum polarization alignment the signal to noise ratio of output 185 relative to a maximum signal to noise ratio of output 185 obtained with an offset angle of 45° is given by:


where [S/N]_(DC)(Δ θ) is the signal to noise ratio of output 185 due to an error rotation angle of Δθ and [S/N]_(DC)(45°) is the signal to noise ratio of output 185 due to an error rotation angle of 45°) and ≈ means approximately equal to.

[0035] At the output of band-pass filter 120 the following equation is valid:


where [S/N]_{(IF Co-Pol)}(45°) is the signal to noise ratio of output 130 information bandwidth at offset rotation angle of 45°, [SIN](0°)_(IFCo-Pol) is the signal to noise ratio of output 130 information bandwidth at offset rotation angle of 0° and 3dB_(45°) denotes a reduction in the signal to noise ratio by 3dB due to a rotation angle of 45°.

[0036] The following equation is also valid:


where DW is the signal bandwidth of output 130, DW1 is the bandwidth of band-pass filter 120 and DW2 is the bandwidth of low-pass filter 180 and

where 3dB_(Mixer) is the reduction in the signal to noise ratio by 3dB due to an insertion loss of mixer 165.

[0037] Substituting equation 4 into equation 3 gives:

[0038] The following algebraic relationship is valid:

[0039] Equation 6 can be rearranged to give:

[0040] As mentioned above with relation to Fig. 4, the bandwidth of band-pass filter 120 is typically in the range 6 MHz to 8 MHz therefore:

[0041] Now, assuming a worst case of DW/DW1 = 0.1 = -10dB, then:

[0042] Now, assuming a worst case of [S/N]_{(IF Co.Pol)}(0°) = 10dB and substituting equation 9 into equation 5, gives:


Equation 1 is rearranged giving:


Therefore, by substituting equation 11 into equation 10, assuming a worse case scenario the signal to noise ratio of output 185 due to an error rotation angle of Δθ is given by:


As the practical threshold level for error detection in the polarization alignment is a signal to noise ratio of 1 to I, which is 0dB, then for the traditional polarization alignment method, based on received satellite signal strength alone, the relative change above threshold due to a small offset rotation angle of Δθ is given by approximately:

[0043] Therefore, it can be seen that the autocorrelation method results in more than 40dB increase in the signal to noise ratio as compared to the traditional signal-strength pointing method. The results are shown in the table of Fig. 5. The second column of the table represents the results of the autocorrelation method based on equation 12 and the third column of the table represents the results of the traditional signal-strength pointing method based on equation 13.

[0044] Reference is now made to Fig. 6, which is a schematic representation of the operation of alignment control system 75 for use with the autocorrelation apparatus 65. In block 190, output 185 being the result of autocorrelation is processed. This process includes checking an autocorrelation result storage area 195 for a prior stored result of autocorrelation. If there is no prior stored result of autocorrelation, the processor decides on an initial estimated adjustment command for alignment actuator 80. The process continues with block 200. In block 200, new data is stored. Newly received result of autocorrelation is stored in autocorrelation result storage area 195. The initial adjustment command for alignment actuator 80 is stored in an actuator command storage area 205. In block 210, an actuator controller sends the initial adjustment command to alignment actuator 80. Alignment actuator 80 adjusts polarization axes 25, 30.

[0045] After the initial adjustment has been made a new result of autocorrelation is received. The process continues at block 190. In block 190, autocorrelation result storage area 195 is checked for a prior stored result of autocorrelation. The prior stored result is retrieved and compared to the newly received result of autocorrelation. If the new result is less than the prior result, alignment actuator 80 will be instructed to continue adjusting in the same direction. If the new result is greater than the prior result, alignment actuator 80 will be instructed to adjust in an opposing direction. The prior actuator command is retrieved from actuator command storage area 205. A new actuator adjustment command is calculated. The process continues with block 200. In block 200, new data is stored. The newly received result of autocorrelation is stored in autocorrelation result storage area 195. The new adjustment command is stored in an actuator command storage area 205. In block 210, actuator controller sends the new adjustment command to alignment actuator 80. Alignment actuator 80 adjusts polarization axes 25, 30. This process continues repeatedly at block 190 until output 185 being the result of autocorrelation approaches zero.

Claims

1. A method for aligning antenna (17) polarization axes (25, 30) of a dual polarized end-user terminal (10) having an antenna (17), the antenna (17) being aligned toward a satellite (20) in relation to azimuth and elevation, the end-user terminal (10) being configured to produce a first output (40) corresponding to a first component (45) of a received signal (15) parallel to a first polarization axis (25) of the antenna (17) and a second output (50) corresponding to a second component (55) of the received signal (15) parallel to a second polarization axis (30) of the antenna (17), the first polarization axis (25) being orthogonal to the second polarization axis (30), the method comprising the steps of:

(a) receiving a linearly polarized signal (15) having a frequency wherein for said frequency and during a time period when said signal (15) is being transmitted, the satellite (20) is not transmitting signals with a linear polarization that is orthogonal to said linearly polarized signal (15);

(b) autocorrelating the first output (40) and the second output (50) to produce a measurement of autocorrelation by inputting said first output (40) and said second output (50) into an electronic mixer (165) and inputting the output of said electronic mixer (165) into a low-pass filter (180) to produce said measurement of autocorrelation; and

(c) adjusting the antenna (17) polarization axes (25, 30) to minimize said measurement of autocorrelation.

2. The method of claim 1 further comprising the step of reducing proportionately frequencies of said first output (40) and said second output (50).

3. The method of claim 2 further comprising the step of tuning said first output (40) and said second output (50) to said frequency.

4. The method of claim 2 further comprising the step of filtering said first output (40) using a first band pass filter (120) and said second output (50) using a second band pass filter (125).

5. The method of claim 1 further comprising, after said step of autocorrelating, the step of displaying said measurement of autocorrelation.

6. The method of claim 1 wherein said step of adjusting is performed by actuating an alignment actuator (80) configured to adjust the antenna polarization axes (25, 30) to minimize said measurement of autocorrelation.

7. A system for aligning antenna polarization axes (25, 30) of a dual polarized end-user terminal (10) having an antenna (17), the antenna (17) being aligned toward a satellite (20) in relation to azimuth and elevation, the end-user terminal (10) being configured to produce a first output (40) corresponding to a first component (45) of a received signal (15) parallel to a first polarization axis (25) of the antenna (17) and a second output (50) corresponding to a second component (55) of the received signal (15) parallel to a second polarization axis (30) of the antenna (17), the first polarization axis (25) being orthogonal to the second polarization axis (30), the system comprising:

(a) a first connection configured for connection to the end-user terminal (10) for receiving the first output (40);

(b) a second connection configured for connection to the end-user terminal (10) for receiving the second output (50); and

(c) an autocorrelation apparatus (65) having a first input and a second input; wherein said first connection is connected to said first input and said second connection is connected to said second input, said autocorrelation apparatus (65) further including a low-pass filter (180) having an input, and an electronic mixer (165) having a first input that is connected to said first connection, a second input that is connected to said second connection and an output that is connected to said input of said low-pass filter (180).

8. The system of claim 7, further comprising a display (70) having an input and wherein:

(a) said low-pass filter (180) has an output; and

(b) the input of a display is connected to said output of said low-pass filter (180).

9. The system of claim 7, wherein:

(a) said autocorrelation apparatus (65) further includes a dual polarized block down-converter having a first input (40) that is connected to said first connection and a second input (50) that is connected to said second connection; and

(b) said dual polarized block down-converter is interposed between said first connection, said second connection and said electronic mixer (165).

10. The system of claim 7, wherein said autocorrelation apparatus (65) further includes:

(a) a first down-converter (85) that is interposed between said first connection and said electronic mixer (165); and

(b) a second down-converter that is interposed between said second connection and said electrode mixer (165).

11. The system of claim 7, wherein said autocorrelation apparatus (65) includes:

(a) a first tuner (100) that is interposed between said first connection and said electronic mixer (165); and

(b) a second tuner (105) that is interposed between said second connection and said electronic mixer (165).

12. The system of claim 7, wherein said autocorrelation apparatus (65) includes:

(a) a first band pass filter (120) that is interposed between said first connection and said electronic mixer (165); and

(b) a second band pass filter (125) that is interposed between said second connection and said electronic mixer (165).

13. The system of claim 7, further comprising an alignment control system (75) and an alignment actuator (80) wherein said alignment control system (75) is configured to control said alignment actuator (80) to adjust the antenna (17) polarization axes (25, 30) in response to an output of said autocorrelation apparatus (65).

Ansprüche

1. Ein Verfahren zur Ausrichtung von Antennen (17)- Polarisierungsachsen (25, 30) einer doppelpolarisierten Endbenutzer-Station (10), die eine Antenne (17) hat, wobei die Antenne (17) im Hinblick auf Azimut und Elevation auf einen Satelliten (20) ausgerichtet wird, wobei die Endbenutzer-Station (10) ausgebildet ist, um eine erste Ausgabe (40) zu erzeugen, die einer ersten Komponente (45) eines empfangenen Signals (15), parallel zu einer ersten Polarisierungsachse (25) der Antenne (17), entspricht, und um eine zweite Ausgabe (50) zu erzeugen, die einer zweiten Komponente (55) des empfangenen Signals (15), parallel zu einer zweiten Polarisierungsachse (30) der Antenne (17), entspricht, wobei die erste Polarisierungsachse (25) orthogonal zur zweiten Polarisierungsachse (30) ist, wobei das Verfahren folgende Schritte umfaßt:

(a) Empfang eines linear polarisierten Signals (15) mit einer Frequenz, worin für diese Frequenz und während eines Zeitraums, wenn das Signal (15) übertragen wird, der Satellit (20) Signale mit einer linearen Polarisierung, die orthogonal zum linear polarisierten Signal (15) ist, nicht überträgt;

(b) Autokorrelation der ersten Ausgabe (40) und der zweiten Ausgabe (50), um eine Messung der Autokorrelation zu erzeugen, durch Eingabe der ersten Ausgabe (40) und der zweiten Ausgabe (50) in einen elektronischen Mischer (165) und Eingeben der Ausgabe des elektronischen Mischers (165) in einen Tiefpaßfilter (180), um die Messung der Autokorrelation zu erzeugen; und

(c) Einstellen der Antennen (17)-Polarisierungsachsen (25, 30), um die Messung der Autokorrelation zu minimieren.

2. Das Verfahren von Anspruch 1, das weiter den Schritt der proportionalen Reduzierung der Frequenzen der ersten Ausgabe (40) und der zweiten Ausgabe (50) umfaßt.

3. Das Verfahren von Anspruch 2, das weiter den Schritt des Abstimmens der ersten Ausgabe (40) und der zweiten Ausgabe (50) auf die Frequenz umfaßt.

4. Das Verfahren von Anspruch 2, das weiter den Schritt des Filterns der ersten Ausgabe (40) mit Hilfe eines ersten Bandpassfilters (120) und der zweiten Ausgabe (50) mit Hilfe eines zweiten Bandpassfilters (125) umfaßt.

5. Das Verfahren von Anspruch 1, das weiter nach dem Schritt der Autokorrelation den Schritt des Anzeigens der Autokorrelationsmessung umfaßt.

6. Das Verfahren von Anspruch 1, worin der Schritt des Einstellens durchgeführt wird durch Betätigung eines Ausrichtungs-Aktuators (80), der ausgebildet ist, um die Antennen-Polarisierungsachsen (25, 30) einzustellen, um die Messung der Autokorrelation zu minimieren.

7. Ein System zur Ausrichtung von Antennen-Polarisierungsachsen (25, 30) einer doppelpolarisierten Endbenutzer-Station (10), die eine Antenne (17) hat, wobei die Antenne (17) im Hinblick auf Azimut und Elevation auf einen Satelliten (20) ausgerichtet ist, wobei die Endbenutzer-Station (10) ausgebildet ist, um eine erste Ausgabe (40) zu erzeugen, die einer ersten Komponente (45) eines empfangenen Signals (15), parallel zu einer ersten Polarisierungsachse (25) der Antenne (17), entspricht, und um eine zweite Ausgabe (50) zu erzeugen, die einer zweiten Komponente (55) des empfangenen Signals (15), parallel zu einer zweiten Polarisierungsachse (30) der Antenne (17), entspricht, wobei die erste Polarisierungsachse (25) orthogonal zur zweiten Polarisierungsachse (30) ist, wobei das System folgendes umfaßt:

(a) eine erste Verbindung, ausgebildet zur Verbindung mit der Endbenutzer-Station (10), um die erste Ausgabe (40) zu empfangen;

(b) eine zweite Verbindung, ausgebildet zur Verbindung mit der Endbenutzer-Station (10), um die zweite Ausgabe (50) zu empfangen; und

(c) eine Autokorrelationsvorrichtung (65) mit einer ersten Eingabe und einer zweiten Eingabe, worin die erste Verbindung mit der ersten Eingabe verbunden ist und die zweite Verbindung mit der zweiten Eingabe verbunden ist, wobei die Autokorrelationsvorrichtung (65) weiter einen Tiefpassfilter (180) mit einer Eingabe einschließt und einen elektronischen Mischer (165) mit einer ersten Eingabe, die mit der ersten Verbindung verbunden ist, einer zweiten Eingabe, die mit der zweiten Verbindung verbunden ist, und einer Ausgabe, die mit der Eingabe des Tiefpassfilters (180) verbunden ist.

8. Das System von Anspruch 7, das weiter eine Anzeige (70) mit einee Eingabe umfaßt und worin:

(a) der Tiefpassfilter (180) eine Ausgabe hat; und

(b) die Eingabe einer Anzeige mit der Ausgabe des Tiefpassfilters (180) verbunden ist.

9. Das System von Anspruch 7, worin:

(a) die Autokorrelationsvorrichtung (65) weiter einen doppelpolarisierten Block-Abwärtsumsetzer mit einer ersten Eingabe (40) einschließt, die mit der ersten Verbindung verbunden ist, und einer zweite Eingabe (50), die mit der zweiten Verbindung verbunden ist; und

(b) der doppelpolarisierte Block-Abwärtsumsetzer zwischen der ersten Verbindung, der zweiten Verbindung und dem elektronischen Mischer (165) angeordnet ist.

10. Das System von Anspruch 7, worin die Autokorrelationsvorrichtung (65) weiter folgendes einschließt:

(a) einen ersten Abwärtsumsetzer (85), der zwischen der ersten Verbindung und dem elektronischen Mischer (165) angeordnet ist; und

(b) einen zweiten Abwärtsumsetzer, der zwischen der zweiten Verbindung und dem elektronischen Mischer (165) angeordnet ist.

11. Das System von Anspruch 7, worin die Autokorrelationsvorrichtung (65) folgendes einschließt:

(a) einen ersten Empfänger (100), der zwischen der ersten Verbindung und dem elektronischen Mischer (165) angeordnet ist; und

(b) einen zweiten Empfänger (105), der zwischen der zweiten Verbindung und dem elektronischen Mischer (165) angeordnet ist.

12. Das System von Anspruch 7, worin die Autokorrelationsvorrichtung (65) folgendes einschließt:

(a) einen ersten Bandpassfilter (120), der zwischen der ersten Verbindung und dem elektronischen Mischer (165) angeordnet ist; und

(b) einen zweiten Bandpassfilter (125), der zwischen der zweiten Verbindung und dem elektronischen Mischer (165) angeordnet ist.

13. Das System von Anspruch 7, das weiter ein Ausrichtungs-Steuersystem (75) und einen Ausrichtungs-Aktuator (80) umfaßt, worin das Ausrichtungs-Steuersystem (75) ausgebildet ist, um den Ausrichtungs-Aktuator (80) zu steuern, um die Antennen (17)-Polarisierungsachsen (25, 30) als Reaktion auf eine Ausgabe der Autokorrelationsvorrichtung (65) einzustellen.

Revendications

1. Procédé pour aligner des axes de polarisation (25,30) d'une antenne (17) d'un terminal (10) d'un utilisateur final à double polarisation et ayant une antenne (17), l'antenne (17) étant alignée vers un satellite (20) selon un azimut et une élévation, le terminal (10) de l'utilisateur final étant configuré pour produire une première sortie (40) correspondant à une première composante (45) d'un signal reçu (15) parallèle à un premier axe de polarisation (25) de l'antenne (17) et une seconde sortie (50) correspondant à une seconde composante (55) du signal reçu (15) parallèle à un second axe de polarisation (30) de l'antenne (17), le premier axe de polarisation (25) étant orthogonal au second axe de polarisation (30), le procédé comprenant les deux étapes de :

a) recevoir un signal polarisé linéairement (15) et ayant une fréquence dans laquelle pour ladite fréquence et pendant une période où ledit signal (15) est en cours de transmission, le satellite (20) ne transmet pas des signaux avec une polarisation linéaire qui est orthogonale audit signal polarisé linéairement (15) ;

b) autocorréler la première sortie (40) et la seconde sortie (50) pour produire une mesure d'autocorrélation en appliquant ladite première sortie (40) et ladite deuxième sortie (50) sur un mixeur électronique (165) et en appliquant la sortie dudit mixeur électronique (165) sur un filtre passe-bas (180) pour produire ladite mesure d'autoborrélation ; et

c) ajuster les axes de polarisation (25,30) de l'antenne (17) pour minimiser ladite mesure d'auto corrélation.

2. Procédé selon la revendication 1 comprenant en outre l'étape de réduction proportionnelle des fréquences de ladite première sortie (40) et de ladite deuxième sortie (50).

3. Procédé selon la revendication 2 comprenant en outre l'étape consistant à accorder ladite première sortie (40) et ladite deuxième sortie (50) à ladite fréquence.

4. Procédé selon la revendication 2 comprenant en outre l'étape de filtrage de ladite première sortie (40) en utilisant un premier filtre passe bande (120) et ladite deuxième sortie (50) en utilisant un second filtre passe bande (125).

5. Procédé selon que la revendication 1, comprenant en outre, après ladite étape d'autocorrélation, l'étape d'affichage de ladite mesure d'autocorrélation.

6. Procédé selon la revendication 1, dans lequel ladite étape d'ajustement est réalisée en actionnant un actionneur d'alignement (80) configuré pour ajuster les axes de polarisation de l'antenne (25,30) pour minimiser ladite mesure d'auto corrélation.

7. Système pour aligner des axes de polarisation (25,30) d'une antenne d'un terminal (10) à double polarisation d'un utilisateur final ayant une antenne (17), l'antenne (17) étant alignée vers un satellite (20) selon un azimut et une élévation, le terminal (10) d'utilisateur final étant configuré pour produire une première sortie (40) correspondant à une première composante (45) d'un signal reçu (15) parallèle à un premier axe de polarisation (25) de l'antenne (17) et une deuxième sortie (50) correspondant à une deuxième composante (55) du signal reçu (15) parallèle à un deuxième axe de polarisation (30) de l'antenne (17), le premier axe de polarisation (25) étant orthogonal au deuxième axe de polarisation (30), le système comprenant :

a) une première connexion configurée pour connecter le terminal (10) de l'utilisateur final pour recevoir la première sortie (40) ;

b) une deuxième connexion configurée pour connecter le terminal (10) de l'utilisateur final pour recevoir la deuxième sortie (50); et

c) un d'appareil d'autocorrélation (65) ayant une première entrée et une deuxième entrée, dans lequel ladite première connexion est connectée à ladite première entrée et ladite deuxième connexion est connectée à ladite deuxième entrée, ledit appareil d'autocorrélation (65) incluant en outre un filtre passe bas (180) ayant une entrée, et un mixeur électronique (165) ayant une première entrée qui est connectée à ladite première connexion, une deuxième entrée qui est connectée à ladite deuxième connexion et une sortie qui est connectée à ladite entrée dudit filtre passe-bas (180).

8. Système selon la revendication 7, comprenant en outre un afficheur (70) ayant une entrée et dans lequel :

a) ledit filtre passe bas (180) a une sortie ; et

b) l'entrée d'un afficheur est connectée à ladite sortie dudit filtre passe bas (180).

9. Système selon la revendication 7, dans lequel :

a) ledit appareil d'autocorrélation (65) comprend en outre un convertisseur abaisseur de fréquence en bloc à double polarisation ayant une première entrée (40) qui est connectée à ladite première connexion et une deuxième entrée (50) qui est connectée à ladite deuxième connexion ; et

b) ledit convertisseur abaisseur de fréquence en bloc à double polarisation est interposé entre ladite première connexion, ladite deuxième connexion et ledit mixeur électronique (165).

10. Système selon la revendication 7, dans lequel ledit appareil d'autocorrélation (65) comprend en outra :

a) un premier convertisseur abaisseur de fréquence (85) qui est interposé entre ladite première connexion et ledit mixeur électronique (165) ; et

b) un deuxième convertisseur abaisseur de fréquence qui est interposé entre ladite deuxième connexion et ledit mixeur électronique (165).

11. Système selon la revendication 7, dans lequel ledit appareil d'autocorrélation (65) inclut:

a) un premier syntoniseur (100) qui est interposé entre ladite première connexion et ledit mixeur électronique (165) ; et

b) un deuxième syntoniseur (105) qui est interposé entre ladite deuxième connexion et ledit mixeur électronique (165).

12. Système selon la revendication 7, dans lequel ledit appareil d'autocorrélation (65) inclut :

a) un premier filtre passe bande (120) qui est interposé entre ladite première connexion et ledit mixeur électronique (165) ; et

b) un deuxième filtre passe bande (125) qui est interposé entre ladite deuxième connexion et ledit mixeur électronique (165).

13. Système selon la revendication 7, comprenant en outre un système de contrôle d'alignement (75) et un actionneur d'alignement (80) dans lequel ledit système de contrôle d'alignement (75) est configuré pour contrôler ledit actionneur d'alignement (80) pour ajuster les axes de polarisation (25,30) de l'antenne (17) en réponse à une sortie dudit appareil d'autocorrélation (65).

Drawing